Besides host phylogenetic assortment, gut microbial community composition in primates is under the influence of a wide set of factors, including diet and subsistence strategy. However, our understanding of microbial functional adaptations in response to these forces, within single and multiple primate species and populations, remains poorly understood. Here, we present functional gut microbiome data generated from fecal samples of a population of western lowland gorillas (G. g. gorilla), hunter-gatherers and traditional agriculturalists in the Dzanga Sangha protected areas, Central African Republic, to show that microbiome changes associated with seasonality in G. g. gorilla are analogous to distinctions observed between the two human populations. Specifically, the data show that dry season gut microbiomes in gorillas exhibit similar functional traits to those observed in hunter-gatherers; whereas reliance on more digestible diets during the wet season shows convergence of microbe metabolic pathways with traditional agriculturalists. The parallel functional changes seen in the gut microbiome of these divergent primate species, particularly exposes microbial genes involved in carbohydrate metabolism, xenobiotics degradation and antibiotic resistance. In showing this parallel, we argue that the gut microbiome of different, but closely related hominids exhibit similar functional adaptations to analogous dietary stimuli, which points to core microbiome contributions impacting metabolic adaptations to dietary and ecological challenges in primates.